"The First World War is a detective story with no resolution for a very simple reason.

"It's what converts a controlled explosion into a monumental explosion that is the real question. Why Austria-Hungary wanted to punish Serbia for the assassination of Archduke Ferdinand is a question that we can answer.

"On the Sixth of July, there was a German-Austrian understanding about how Germany would support Austrian attempts to annihilate Serbia. We know that. That's not the detective story. The story is how did you get from there to the First World War, and who wanted that small explosion to become a big one? And the answer is almost impossible to define.

"There are those who say that the German military and navy wanted it for years. This was their grasp for world power. This is the moment of truth, when they finally get what they should have gotten because of their economic industrial power. That means it's all malice aforethought, and the whole story is cooked up in Berlin.

"There are other people who say they wanted a small-scale war, and got a big scale war instead, and lost it.

"But there's a third view that it is, as it were, a collective failure. As you said, the collective failure is that individuals who are diplomats, and with the intention of stopping these conflicts from getting out of hand simply didn't take it seriously enough, on both sides of the line.

"I would have thought that the best way to understand this question of who was responsible for the outbreak of the First World War is to eliminate those of lesser responsibility. Nobody in London, nobody in Paris, nobody in St. Petersburg wanted the small war to turn into a big war. That conversion of the Balkan War into the Great War was not conjured up anywhere other than in Berlin and in Vienna.

"If there is a smoking gun, it's in one or the other of those capitals. But the jury's still out. The trial has yet to be concluded."